newby with crankcase pressure blowby???

[minitruckpig]

First and foremost Thank you to everyone on Ratsun.You guys have helped me out alot.Well i aquired a l20b out of a 510 to put in my 620.Dual side draft 40 dcoe carbs,cannon intake,peanut head,flat top pistons,not sure what else is in it.did a pressure test cylinder 1,210 2,3 and 4 where between 125 and 135.I was unable to use the 40 dcoes because they hit the brake booster.:mad: So i threw my down draft on there got it to start and the vent tube on the valve cover was spitting oil out like it was going out of style.The crankcase tube on the intake side of the motor has been cut and welded shut.Is that correct???OHH yeah i did a leak down test too and it held the pressure over night.also adjusted valves .008 and .010(Thanks hainz)Any help or suggestions would be greatly appreciated.Thanks guys

[banzai510(hainz)]

The crankcase tube on the intake side of the motor has been cut and welded shut.Is that correct

 

Thats a BIG NO NO!!!!!!!!!!!!!!!!!!

 

at idle it will Vent OUT. like its supposed to . Well mine does. So I assume the air has to go out somewhere.

then when you rev up it will suck IN

 

I run mine oepn vent. Meaning My vent tube just stucks out.

 

if i run a Weber DGV down draft I usually hook up the crank case vent to the lower part of the intake manifold(PCV valve)

 

 

If truely a L20 with flatops it should have higher #s.

 

 

on the sidedrafts will it fit if you take the last airhorn off???????

 

 

olddatsuns.com

Edited June 8, 2009 by banzai510(hainz)

[minitruckpig]

I was going to take that off but i was told the horn held in part of the carb.Ill open that vent tube and try a wet compression test.Hainz your video is great.If your ever in dfw area dinner and drinks are on me.:D

[banzai510(hainz)]

I dont know Webers but all I can say its 2 hex nuts or small bolt that hold the HORN on there.

 

Open that crank case vent!!!!!!!!!!!

[datzenmike]

Even if you fix the PCV it won't help those low 2,3,4 numbers. An L20B with flat tops and p nut should have about 10.75 compression. That's probably well over 200PSI when cranking. That motor's getting tired I'm afraid.

[ggzilla]

Yes. 210 psi and 135 psi don't mix. It means your rings are shot.

[minitruckpig]

well the rings our probably shot this was a fresh motor build before i got it the big problem i have recently discoverd is that it sat for a few years after the build im thinkin the rings seized against the cylinder walls and ate them selves up possibly.Whenever i get A day off ill find out for sure.Until then thanks guys!!

[72240z]

I would open that crank vent and re comp test, engines sit for years all the time and the rings aren't shot.

 

That must have been a sight too, welded the vent shut, crazy lmao.

[yello620]

I would open that crank vent and re comp test, engines sit for years all the time and the rings aren't shot.

QUOTE]

 

I would also make sure that the throttle is opened up to let air into the motor to compress it. If the cylinder cant get any new air, it sure cant compress it.

 

Disconnect the coil and prop the throttle open, then retest it.

 

Good Luck

[minitruckpig]

thanks guys i will try that.

[datzenmike]

If you drive it the compression may come up some.... but don't hold your breath. If it was rebuilt it may have been done poorly or had the shit driven out of it..... anyone who would weld up the PCV doesn't know what they are doing. Maybe the poor performance is why it was sold. Hope you didn't pay too much for a core motor.

[minitruckpig]

Well luckily I traded a bunch of car audio equipment and built a box installed everything to aquire the drivetrain.The guy i got it from was real honest about it.I also got a dogleg out of the deal which shifts great.Hopefully i wont lose my mind at Freeway speeds now.

[DISLEXICDIME]

if you are running a dog leg with a l20 b with flat tops webers and a peanut head don't beat on it to much or the dog leg will fail they are not very strong

[datzenmike]

I've said the same thing based on the gear and bearing sizes in them.... had some people tell me in no uncertain tern this isn't so. I would have to say that everyone drives differently. If you have an L20B/flat tops/Webers/p-nut head and drive it like you stole it it will wear out faster than an FS5W71B tranny and IT will wear out faster than an FS5W71C tranny, and IT will wear out faster than an FS5R30A. And here it stops with an indestructible tranny. :D

 

If you just drive it, almost any tranny will last a long time.

[DISLEXICDIME]

i fried mine in 2 weeks.:( i have destroyed all the datsun tranies except the original 4 speed that was in my dime i wish i still had it. I am not braging by any means. i am sick of swapping trany's in to this car. but it is so mutch fun steering with the rear in my dime. I am giving either a z car or a truck 5 speed one more chance. Then if wich ever one i choose to put in brakes! I am going to try a ka trans with a l bell housing

 

ps i do drive it like i stole it! Thats what i built it for. lol

[sssr20det510]

i fried mine in 2 weeks.:( i have destroyed all the datsun tranies except the original 4 speed that was in my dime i wish i still had it. I am not braging by any means. i am sick of swapping trany's in to this car. but it is so mutch fun steering with the rear in my dime. I am giving either a z car or a truck 5 speed one more chance. Then if wich ever one i choose to put in brakes! I am going to try a ka trans with a l bell housing

 

ps i do drive it like i stole it! Thats what i built it for. lol

 

I blew up four 4 speeds before i swapped out to a z 5 speed in my l20b 510

[datzenmike]

i fried mine in 2 weeks.:( i have destroyed all the datsun tranies except the original 4 speed that was in my dime i wish i still had it. I am not braging by any means. i am sick of swapping trany's in to this car. but it is so mutch fun steering with the rear in my dime. I am giving either a z car or a truck 5 speed one more chance. Then if wich ever one i choose to put in brakes! I am going to try a ka trans with a l bell housing

 

ps i do drive it like i stole it! Thats what i built it for. lol

 

While you're driving it, start your L/KA hybrid. :lol:

[minitruckpig]

call me crazy i dont see that ka mixing with a l series :lol: :lol:

[72240z]

call me crazy i dont see that ka mixing with a l series :lol: :lol:

 

Crazy :rolleyes:

[datzenmike]

call me crazy i dont see that ka mixing with a l series :lol: :lol:

 

OK... but the front case from any FS5W71B (even the F4W71B 4spd will work) will bolt to the KA FS5W71C tranny. You will likely need to swap the front counter gear and drill out the 1st/2nd shift rod hole in the L case, but it will fit and convert a KA 'C' type for use on an L motor.

[minitruckpig]

crazy i am.Well i opened up the crankcase vent.Still have crazy case pressure.Got A lil frustrated and decided to pull the motor out and go through it.Im really starting to wonder what is actually in this motor.Thanks again everyone.whenever I get A day off I will let you know what I find.

[banzai510(hainz)]

At idle its normal for AIR to come out. But NOT spitting out unless the vent cover was remove in the valve cover.

 

What I do is route a water line size hose to under the car so it spits its exess to the ground instead of the firewall of car

[72240z]

I just want to suggest a catch canister of some kind so you don't leave a shit stain everywhere you idle lol.

[minitruckpig]

WELL I GOT THE MOTOR APART LAST NIGHT AND CYLINDERS 2 3 4 ALL HAD TAP MARKS ON THE PISTONS FROM THE VALVES.(THOSE WHERE THE ONES WITH 125 TO 140 COMPRESSION):mad: WHOEVER ASSEMBLED THIS MOTOR DIDNT TIME IT CORRECTLY OR MAYBE THE DECK HEIGHT IS OFF.ILL TRY AND POST SOME PICS UP LATER TODAY

[banzai510(hainz)]

you could have cked the cam timming before tearing it apart.

if it was timed correctly then what would make those hit in the pistons. HUGE HUGE CAM.???????